Improve Heat Resistance of Composite Engine Cowlings Using Ceramic Coating Materials, Experimental Design and Testing

A large amount of heat generated in the engineering compartment in a hovering helicopter may lead to premature degradation of inner skin of its engine cowling and cause serious failure on the engine cowling. This study proposes a solution of improving heat resistance of the helicopter engine cowlings by replacing the currently used intumescent coating with a ceramic coating material, Cerakote C-7700Q. Oven and flame tests were designed and conducted to evaluate the heat resistance of Cerakote C-7700Q. The test results show that the currently used painting scheme of the engine cowlings failed the 220°C oven test while after replacing the epoxy seal coat with the Cerakote, the new painting system passed the 220°C test in regards to painting bubbling. Based on that, a new painting scheme with C-7700Q implemented was recommended. It is suggested that the most time- and cost-effective solution to improve thermal performance of the helicopter engine cowlings is to repaint the current engine cowlings with the proposed new three coating system of Cerakote, surface protection HS7072-622, and intumescent paint as a fireproof lacquer. This study also explains why serious appearance defects occurred in the inner skin of the engine cowling when the aircraft is hovering. The present work can be converted to a design project for senior mechanical engineering students to develop their design and teamwork skills and enhance their capacity for solving real-world engineering problems.